Digital communication based arc control welding system and method

ABSTRACT

A welding system includes components equipped with digital communications circuitry for synchronization and coordination of tasks associated with the welding operation. The tasks may be initiated and terminated independently or in coordination based upon synchronization of this circuitry. Certain of the tasks may be performed by the components in an open-loop manner or in a closed-loop manner based upon feedback of welding parameters. Moreover, certain tasks may be independent of one another, or interdependent although carried out in parallel by the different system component.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Non-Provisional patent application of U.S.Provisional Patent Application No. 61/508,413, entitled “DigitalCommunication Based Arc Control Welding System and Method”, filed Jul.15, 2011, which is herein incorporated by reference.

BACKGROUND

The invention relates generally to welding systems, and moreparticularly to improved techniques for effective control of weldingarcs through digital control and coordination of system components.

A number of welding systems and processes have been developed and arecurrently in use. In general, these involve creation of an arc betweenan electrode and a work piece, which serves to melt filler metal and thework piece. These refuse to establish the desired joint. In someprocesses, such as gas metal arc welding (GMAW), a subset of which iscommonly called metal inert gas (MIG) welding, flux-cored arc welding(FCAW), and shielded metal arc welding (SMAW), commonly called “stick”welding, the electrode itself is melted and becomes part of the weld. Inother processes, such as gas tungsten arc welding (GTAW), commonlycalled tungsten inert gas (TIG), an electrode is not melted, but servesonly to sustain an arc that melts the work piece and separate addermetal, when used.

In all of these welding processes, power supplies are used, along withother components, the construction and operation of which may vary basedupon the type of process, and the way it is carried out. For example, inMIG systems, a power supply is generally coupled to a wire feeder thatprovides a controlled supply of welding wire electrode through a weldinggun. The power supply or wire feeder is also typically coupled to asupply of shielding gas. In both MIG and TIG systems, moreover, thepower us ultimately supplied to a welding gun or torch, used to completethe electrical circuit for the welding arc.

Control of such welding systems is typically based on feedback ofvarious measured parameters, with open loop control of others. Forexample, currents and/or voltages are often measured, and used as abasis for closed loop control of pulses, output power levels, and soforth, as dictated by the particular welding regime selected. Othersettings, such as wire feed speeds, may be essentially open loop,although there, too, tachometer readings, motor drive voltages, andsimilar parameters may be sensed and/or controlled in closed loopmanners.

Conventional control schemes of this type, while very effective inproviding high quality welds, are subject to certain drawbacks. Inparticular, the reliance of feedback for much of the process controlmakes the systems inherently reactive, resulting in delays that simplycannot be avoided due to the nature of the communication and controlapproach. Only limited improvements can be made, such as through fastersignal transfer, higher processing speeds, and so forth, although thesetoo have inherent limits.

There is a need, therefore, for improved techniques for control ofwelding processes that can reduce delays and improve the weldingoperations.

BRIEF DESCRIPTION

The present invention provides a novel approach to welding systemcontrol designed to respond to such needs. The approach is based uponsynchronization of operations of welding components, thereby leading tomore determinative control in which certain operations can be scheduledrather than performed based on feedback of sensed parameters. To besure, the system may, and typically will, make use of parameter sensingand feedback, followed by computations and closed loop control, as inconventional welding systems, but the ability to schedule events byvirtue of the proposed synchronization may greatly facilitate theperformance of many tasks in the welding operation. These may beperformed by the different synchronized components, scheduled to operatein parallel, with tasks and closed loop control being advanced followingcertain scheduled operations. It is believed that many options andfuture innovations may flow from the synchronization of the weldingsystem components, particularly once these are freed, at least somewhat,from reactive-only closed loop control.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a diagrammatical representation of a welding system designedfor coordinated synchronization and coordinated operation of systemcomponents in accordance with the present disclosure;

FIG. 2 is a flow chart or timing diagram illustrating execution of taskson various welding system components of the time illustrated in FIG. 1;and

FIG. 3 is a graphical representation of timing of events coordinated inaccordance with FIG. 2.

DETAILED DESCRIPTION

Turning now to the drawings, FIG. 1 represents an exemplary weldingsystem 10 in which synchronization and coordinated tasks may beimplemented for welding operations. The welding system 10 is illustratedas including a welding power supply 12 and a wire feeder 14. The weldingpower supply and the wire feeder provide power and welding services to awelding gun or torch 16. In operation, power and welding wire aresupplied, along with shield and gas, depending upon the application, soas to execute a weld on a work piece 18.

It should be noted, although a MIG welding system is illustrated in FIG.1, the present techniques may be employed with any welding system,welding process, and welding component. Thus, TIG systems, sticksystems, and so forth may utilize similar techniques based upon thepresent disclosure. Moreover, processes may include constant currentprocesses, constant voltage processes, pulse processes, and so forth,and a number of different material transfer modes may be accommodated,such as short circuit transfer, spray transfer, globular transfer, andso forth.

In the illustrated embodiment the welding power supply 12 comprises arccontrol circuitry 20 coupled to gate drive circuitry 22. The arc controlcircuitry is designed to control a welding arc established between thewelding electrode and the work piece, particularly based upon thesynchronized and coordinated control described in the presentdiscussion. In practice, the arc control circuitry may be part of acontroller that performs a number of other functions in the power supplyand the welding system. The arc control circuitry will typically includea microprocessor or digital signal processor and associated memory. Thememory stores pre-defined welding processes, welding parameters, weldsettings, and so forth utilized by the arc control circuitry throughoutthe welding processes. The gate drive circuitry 22 receives signals fromthe arc control circuitry to regulate conductive states of powerelectronic power devices within power conversion circuitry 24. Powercontrol circuitry 24 will be coupled to a source of electrical power,such as the power grid, an engine-drive generator, batteries, fuelcells, or any other suitable power source. In operation, based upon theprocess implemented by the arc control circuitry 20, the gate drivecircuitry 22 will be commanded to provide drive signals to powerelectronic switches within the power conversion circuitry to generatesuitable power for welding. As will be appreciated by those skilled inthe art, such devices may include SCRs, IGBTs, and/or any other suitabledevices. Moreover, the power conversion circuitry may be of the typegenerally found in such systems, including boost converters, buckconverters, power transformers, and so forth. Power created by the powerconversion circuitry is conveyed to the wire feeder as indicated atreference numeral 26, and to a work cable 28 which will typically becoupled to the work piece or to a fixture in which the work piece ispositioned.

The welding power supply further includes digital communicationscircuitry 30 designed to provide synchronized operation with otherwelding system components, such as the wire feeder. The digitalcommunication circuitry may be provided independently of the arc controlcircuitry 20, or may be incorporated with the arc control circuitry intoa single support, circuitry board, and the like. The digitalcommunications circuitry 30 allows for communication of weldingparameters, commands, feedback, and so forth between the welding powersupply and other system components. The circuitry may be adapted tooperate in accordance with known digital communications protocols forsuch communications. In the illustrated embodiment, the digitalcommunications circuitry 30 of the power supply communicates withsimilar digital communications circuitry 32 of the wire feeder. The twodevices allow for synchronization of the operation of the power supplyand wire feeder and will typically include their own clocks providingsignals which may form the basis for this synchronization. In certainembodiments, synchronization may be performed in circuitry withoutseparate clocks. In a presently contemplated embodiment, thecommunications circuitry is synchronized at least every millisecond,although other periods or frequencies of synchronization may be used.

It should also be noted that a welding power supply 12 will typicallyalso include an operator interface (not shown) that allows for userselection of welding processes, weld settings, weld parameters, and soforth, such as current and voltage. Such parameters may be conveyed tothe arc control circuitry 20, stored in memory, and so forth for use incontrolling the welding operation. As also illustrated in FIG. 1, thedigital communication circuitry 30 may allow for communication to remotedevices/automation systems 34. Thus, although a manual MIG system isillustrated, the present techniques may be employed with automated(e.g., robotic) systems in which welding may be fully or partiallyautomated based upon the pre-established programming.

The wire feeder 14 includes motor/motion control circuitry 36 coupled tothe digital communications circuitry 32. In many applications themotor/motion control circuitry 36 will include a separate microprocessoror digital signal processor capable of carrying out operationscoordinated with the welding power supply as described below. Suchprocessors will be associated with memory (not separately shown) whichmay store operational programming, calibration settings, weld settings,operator-input preferences, and so forth. In general, these willinclude, for example, a wire feed speed, but they may also include wiretypes, and the like. The motor/motion control circuitry 36 is configuredto drive a wire from a spool 36 by commanding operation of a motor 40coupled to a drive assembly 42. Such control signals may, for example,take the form of variable voltage signals, and will depend upon thenature of motor 40 and the other components of the system. The wirefeeder 14 is also coupled to a gas supply 44 for providing shield andgas for the welding operation. Accordingly, a valve 46 is provided forallowing a flow of gas to be provided to the welding torch, and forinterrupting the flow. In certain embodiments, the valve may also allowfor some degree of metering. In the illustrated embodiment, the valve iscontrolled by the control circuitry 36.

In operation, the system of FIG. 1 is synchronized by communicationbetween the digital communications circuitry such that weldingoperations may be broken into tasks that can be coordinated between thewelding system components. That is, whereas in conventional systemsoperations are typically performed either in an open-loop manner or in aclosed-loop manner based upon feedback, at least some of the tasksperformed by the components of the welding system as described hereincan be performed on a scheduled basis. FIG. 2 represents circuitry tasksperformed on a welding system of the type illustrated in FIG. 1 in asynchronized and coordinated manner.

As shown in FIG. 2, a welding operation 48 is typically initiated by acommand as indicated by reference numeral 50. This command maycorrespond to an operator depressing a trigger on a welding gun, but mayalso comprise initiation of a welding arc in a stick process or thereceipt of a command from a remote device, such as for automatedoperations. The receipt of the command begins the welding operation asindicated at time 52. In the diagram of FIG. 2, several components areillustrated as performing tasks, some coordinated with other tasks, andothers independent of other tasks. In this illustration, a firstcomponent begins a first task at time 52 as indicated by block 54. Thistask is illustrated as lasting until time 56 at which time a second taskis initiated by the first component as indicated at reference numeral58. It is contemplated that during these times coordination will be madebetween other system components by synchronization of circuitry, such asthe communication circuitry discussed above. In the illustratedembodiment, therefore, a second component begins a first scheduled taskas indicated at block 60. Tasks 58 and 60 continue in parallel untiltime 62. At time 62, the first component carries on a third task 64,while the second component begins a second task 66. At the same time, athird component begins its first task as indicated at block 68.

Following these initialed tasks, the first component is shown tocontinue the third task indefinitely while at times 70 the second andthird components begin tasks 72 and 74 respectively. This point in thecontrol may correspond to steady state welding conditions in the weldingoperation.

Several observations should be made regarding the synchronization andcoordination of these tasks. First, certain of the tasks may bescheduled and coordinated to begin and/or end at the same time. However,certain tasks may end earlier that other tasks performed by othercomponents, and the component with the task ending earlier may beinstructed to wait until a task is completed by another component. Forexample, task 58 may be completed prior to task 60, but component 1 maybe instructed to wait until completion of task 60 to begin itssubsequent task 64. Moreover, it should be noted that some these tasksmay be open-loop operations in which a component is turned off or on, oris commanded to operate at a pre-determined level. Other tasks may beclosed-loop, typically based upon feedback of one or more sensed weldparameters as in current welding systems. This closed-loop operation isillustrated in FIG. 2 by the cyclical arrows in tasks 66, 72 and 74. Itshould be noted, however, that these are merely illustrative, and anyone of the tasks may be at least partially closed-loop for theparticular component. Moreover, any one of the tasks may be completelyindependent of other component tasks, or these may be substantiallyinterdependent. That is, for example, the third task of component 2,indicated by reference numeral 72, may utilize feedback that is alsoutilized by component 3 in performing its scheduled task 74. Suchinterdependence may be common in certain phases of the weldingoperation, such as for coordinated wire feed and power control. Forcoordinated operation, the components may communicate, via the digitalcommunications circuitry, the state of the various tasks, particularlywhen certain tasks are to begin only after completion of other tasks onother components.

As further illustrated in FIG. 2, at some point a command will bereceived to end the welding operation as indicated at reference numeral76. Depending upon the system type and the process performed, this mayconsist of an operator releasing a welding torch trigger, moving a torchor stick away from a work piece to terminate an arc, or an automatedcommand received from a remote device (e.g., to terminate a weld afterreaching a desired location on a work piece). In the illustration ofFIG. 2, this command is received at time 78, at which the firstcomponent begins a scheduled task 80 to begin termination of the weldingoperation. Following termination of this task, the component performsits final task 82. Separately from the performance of the scheduledtasks by the first component, the second component may begin its lastscheduled task at time 86, somewhat after time 78 to begin terminationof the welding operation. In the illustrated embodiment, the thirdcomponent also begins a task at this stage as indicated by referencenumeral 88. These two tasks are illustrated as being completed at time90 and a final task is then performed by the third component asindicated at reference numeral 92. Here again, some or all of thesetasks may open-loop or closed-loop based upon sensed welding parameters.Following completion of all tasks, the welding operation is terminated.

Throughout the processes outlined in FIG. 2, synchronization of thewelding components takes place. Thus, within the time horizon of thesynchronization, the various tasks may be easily coordinated. It shouldbe noted that the command of the tasks may originate in controlcircuitry of each individual component, or certain components maycommand operation of others. However, the present techniques contemplateat least two components having circuitry permitting synchronization andcoordinated tasks. It should also be noted that some or all of the tasksmay be commanded by remote devices, such as that illustrated in FIG. 1,particularly for automated applications. Still further, the tasksperformed by the welding system components, particularly in automatedsettings, may be coordinated with tasks performed by other machinesystems, such as to begin and end welding operations at particularpositions and times based upon location and readiness work pieces,assemblies, and the like on assembly lines and in weld cells.

FIG. 3 is a graphical representation of an exemplary welding process 94of the type summarized in FIG. 2. FIG. 3 represents the welding processin terms of a magnitude or state of the components along access 96 and atime along access 98. In the illustration of FIG. 3, trace 100, then,represents flow of shield and gas under the control of valving (here“component 1”), trace 102 indicates welding wire feed (via control ofthe wire feed motor and assembly, here “component 2”), while trace 104represents the voltage output of the power supply (via control of thepower conversion circuitry, here “component 3”). As can be seen in thefigure, tasks are initiated and completed at particular times for thedesired welding operation.

In particular, at time t0, the welding operation is initiated by thereceipt of a command as described above. From this point, a pre-flow ofshield and gas is begun by control of the gas valve. This task may beperformed open-loop and for a predetermined length of time, followed bya change in the flow rate of the gas as a second task between times t1and t2. At time t2, then, the flow of shield and gas will have reached asteady state level and is not further changed (generally correspondingto the third task 64 illustrated in FIG. 2). Also at time t2, voltageoutput of the power supply is significantly increased to anticipateinitiation of the welding arc. At time t3 the voltage reaches a peak andwelding wire feed is begun as indicated by trace 102. Between times t3and t4, the welding power supply will continue increasing the wire feedrate, and ultimately an arc will be established during this period. Uponestablishment of the arc, the voltage may be reduced as indicated bytrace 104. Here it should be noted that one or both of these operationsmay be performed in a closed-loop manner upon detection of currentsand/or voltages that indicate the establishment of the welding arc. Attime t4, then, the wire feed speed and voltage will reach a steady statelevel, and the welding operation will proceed.

It should be noted that, as mentioned above, any of these tasks andoperations may be substantially interdependent. For example, in certaincases, the wire feed speed may be coordinated with the initiation of thearc and the application of power to sustain the arc. While notillustrated specifically in FIG. 3, many variations on these tasks, withand without feedback control and interdependence between the tasks maybe envisaged.

In the illustration of FIG. 3, the welding operation continues untiltime t5 where a signal is received to terminate the welding operation.This may correspond to, for example, a welding operation releasing atrigger on a welding torch. In the illustrated embodiment, this signalresults in the beginning of a reduction in gas flow until time t6,followed by continuous reduction in gas flow until time t8. As will beappreciated by those skilled in the art, in such operations gas flow maybe continued to sufficiently shield the cooling weld bead and weldpuddle. Here this operation is performed somewhat independently of theoperations performed that affect the wire feed and applied voltage.

At time t7 the rate of wire feed is ramped down, ultimately reaching aterminal point at time t9. The voltage is also ramped down until timet9, at which point the voltage is terminated as indicated at time t10.Here again, these operations may be interdependent, and may be basedupon sentenced welding parameters.

Throughout such processes, it is believed that significant advantagescan be obtained by the ability to schedule tasks of one or more of thewelding system components either independently or dependently. Thesynchronization of the components allows for somewhat parallel operationthat may rely at times upon feedback, and at times upon initiationpoints, terminal points, and so forth. Here again, within each of thetasks, open-loop or closed-loop operation may be implemented, in certainof these may be identical to those of conventional welding systems.However, the synchronization of the schedule-based tasks providesenhanced flexibility and reduces delays in the initiation andtermination of certain operations during the welding operation.

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. A system comprising: a welding power supply configured to producewelding output power suitable for a welding operation, the welding powersupply comprising first digital communications circuitry configured tosend and to receive welding parameters during a welding operation; atleast one other welding component coupled to the welding power supplyand configured to perform a part of the welding operation, the at leastone other welding component comprising second digital communicationscircuitry in communication with the first digital communicationscircuitry and configured to send and to receive the welding parametersduring the welding operation; wherein the first and second digitalcommunications circuitry are synchronized.
 2. The system of claim 1,wherein the welding power supply and the at least one other weldingcomponent are configured to perform tasks during the welding operationthat begin and/or end at the same time coordinated by synchronizationvia the digital communications circuitry.
 3. The system of claim 1,wherein the welding power supply is configured to perform a task duringthe welding operation in a closed-loop manner based upon feedback of awelding parameter.
 4. The system of claim 3, wherein the at least oneother welding component is configured to perform a task during thewelding operation in a closed-loop manner based upon feedback of thesame or a different welding parameter, the task performed by the weldingpower supply being coordinated with the task performed by the at leastone other welding component by synchronization via the digitalcommunications circuitry.
 5. The system of claim 4, wherein the taskperformed by the welding power supply and the task performed by the atleast one other welding component are interdependent.
 6. The system ofclaim 1, wherein the digital communications circuitry is configured tosend data to and to receive data from a remote automation system.
 7. Thesystem of claim 6, wherein the welding operation is at least partiallycommanded by the remote automation system.
 8. The system of claim 1,wherein the digital communications circuitry is configured tosynchronize at least every millisecond.
 9. The system of claim 1,wherein each of the welding power supply and the at least one otherwelding component comprises respective processing circuitry configuredto control tasks synchronized via the digital communications circuitry.10. The system of claim 1, wherein the digital communications circuitryof the welding power supply is configured to communicate with thedigital communications circuitry of the at least one other weldingcomponent communicate with one another via a conductor separate from aconductor used to convey power form the welding power supply.
 11. Thesystem of claim 1, wherein the digital communications circuitry of thewelding power supply is configured to communicate with the digitalcommunications circuitry of the at least one other welding componentcommunicate with one another via a conductor used to convey power formthe welding power supply.
 12. The system of claim 1, wherein the digitalcommunications circuitry of the welding power supply is configured tocommunicate with the digital communications circuitry of the at leastone other welding component communicate with one another wirelessly. 13.A method for controlling a welding system, comprising: synchronizing awelding power supply configured to produce welding output power suitablefor a welding operation with at least one other welding componentcoupled to the welding power supply and configured to perform a part ofthe welding operation; initiating the welding operation; and performingscheduled tasks for the welding operation on the welding power supplyand the at least one other welding component in coordination based uponthe synchronization.
 14. The method of claim 13, wherein a taskperformed by the welding power supply or the at least one other weldingcomponent is performed in an open-loop manner.
 15. The method of claim13, wherein a task performed by the welding power supply or the at leastone other welding component is performed in a closed-loop manner basedupon measured feedback, or estimated feedback, of a welding parameter.16. The method of claim 13, comprising synchronizing the welding powersupply and the at least one other welding component at least everymillisecond.
 17. The method of claim 13, wherein tasks performed by thewelding power supply and by the at least one other welding component arecoordinated to begin and/or to end at the same time.
 18. A weldingsystem comprising: a welding power supply configured to produce weldingoutput power suitable for a welding operation, the welding power supplycomprising first digital communications circuitry configured to send andto receive welding parameters during a welding operation; a welding wirefeeder coupled to the welding power supply and configured to providewelding wire during the welding operation, the wire feeder comprisingsecond digital communications circuitry in communication with the firstdigital communications circuitry and configured to send and to receivethe welding parameters during the welding operation; wherein the firstand second digital communications circuitry are synchronized.
 19. Thesystem of claim 18, wherein at least one task performed by the weldingpower supply and/or the wire feeder is performed in an open-loop manner,and at least one other task performed by the welding power supply and/orthe wire feeder is performed in a closed loop manner based upon feedbackof a welding parameter.
 20. The system of claim 1, comprising valvingfor controlling flow of shielding gas for the welding operation, whereinoperation of the valving is coordinated with provision of power by thewelding power supply and of welding wire by the welding wire feederbased upon synchronization via the digital communications circuitry.